Data storage apparatuses typically provide that some type of data storage medium is rotated as data is read from or written to the data storage medium. For many different reasons, the rotation of the data storage medium usually results in at least some amount of vibration. For example, due to manufacturing tolerances, the data storage medium typically is not perfectly planar. As a result, the disc storage medium may wobble when it is rotated. Of course, the wobble becomes greater with higher speeds of rotation, and increased vibrations are produced. As a consequence of the wobble and vibrations, data may not be able to be retrieved from or written to the data storage medium, or worse, the data storage medium and/or the data storage apparatus may become damaged as a result of rotating the data storage medium.
Vibrations resulting from rotating a data storage medium in a data storage apparatus are particularly prevalent when a data storage apparatus is used to rotate several different data storage media where each data storage medium is removable from the data storage apparatus and is relatively heavy. One example of the foregoing is where the data storage apparatus is used with several different removable data storage media. In this case, due to the different manufacturing tolerances in the industry, the vibrations which will result from rotating a given data storage medium are extremely difficult, if not impossible, to predict.
Additionally, some removable data storage media, such as CD-ROMS, are relatively heavy which causes a substantial amount of inertia when the disc is rotated.
Several other factors may contribute to the vibrations which result from rotating a data storage medium. For example, typically, data storage media, such as a CD-ROM, include a label and/or ink thereon which provides visible indicia relating to the contents of the data storage medium, the source of the data storage medium, etc. Along with manufacturing tolerances, the label and/or ink distribution may provide another source of imbalance when the data storage medium is rotated, and may increase the vibrations resulting from the rotation thereof.
Still more sources of vibrations resulting from rotating a data storage medium, such as CD-ROM, are manufacturing tolerances of the spindle and chuck assembly which chucks, or retains, the data storage medium, and the precision with which the chuck actually engages the data storage medium before and during rotation.
Augmenting the unpredictability of the vibrations resulting from rotating a given data storage medium is the manner in which some data storage devices operate. Some typical data storage devices operate in a Constant Linear Velocity (CLV) mode where the angular velocity of the data storage medium is varied to provide a substantially constant linear velocity of the medium under the data (data read and/or data write) head as the head is moved radially across the disc. Generally, present data storage devices provide a two-and-a-half time speed difference from the slowest angular velocity when the data head is at the outermost portion of the medium to the fastest angular velocity when the data head is at the innermost portion of the medium. Such speed changes inevitably produce different vibration characteristics.
While data storage devices have actually evolved to operate in a modified or zoned Constant Angular Velocity (CAV) mode, such drives span a two to three times difference between the minimum and maximum spindle speeds. Therefore, vibrations are still an issue.
While data storage devices have become faster and faster in recent years, vibrations resulting from rotating a data storage medium have limited the speed at which the medium can be rotated and have limited the rate at which data can be reliably read from or written to the medium. In fact, the overall reliability of a data storage device generally degrades with faster rates of rotation. The emergence of, for example, DVD-ROM drives with a faster data rate for a given comparable spindle rate also requires minimal vibration in order to improve read and writeability. In fact, with the rotation of any data storage medium comes the necessity to counteract the vibrations which result from the rotation in order to read or write data as quickly as possible.